I appear to have a Western Californian seed bug, found on the bathroom basin. I was going to record but it’s not listed. Given the risk of spreading and the damage apparently they cause, I intend to kill it
Assuming what you've found is Leptoglossus occidentalis, then the usual English name is Western Conifer Seed Bug rather than Californian, so it should come up if you try that. They are non-native, I don't think they are particularly a problem here (yet?!) - they are often found around this time of year as they sometimes overwinter in buildings.